JP2016016052A - Artificial hip joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an artificial hip joint having a fluid lubrication film formation function at a fine clearance, and also having little squeaky sound generation or abrasion.SOLUTION: An artificial hip joint includes an acetabular socket 22 having a recessed spherical part 25, and an artificial femoral head 26 having relative sliding contact with the recessed spherical part 25 of the acetabular socket 22, by being fitted therewith. An annular region 31 having a cyclic structure part 32 constituted of a plurality of fine grooves is provided on the artificial femoral head sliding surface 30 of the recessed spherical part 25 of the acetabular socket 22.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an artificial hip joint.

  As shown in FIG. 13, the artificial hip joint is slidable on a acetabular socket 51 attached to the acetabulum of the pelvis, a stem 52 attached to the femur, and a concave ball portion 55 of the acetabular socket 51. And a bone head 53 to be fitted. In addition, the stem 52 and the bone head 53 are connected via a neck portion 54.

  In recent years, wear powder reduction is effective for prolonging the life of artificial hip joints, and therefore, hard-on-hard artificial hip joints made of metal and ceramics are being developed as sliding members with less wear. Sliding in the hip prosthesis is multi-directional, and a static load state occurs irregularly. As a result, ringing occurs and the fluid lubricating film may not be recovered even after unloading. Since ringing causes squeak noise and wear, creation of a functional surface having a fluid lubrication film forming function with a minute clearance is desired.

  Conventionally, as shown in FIG. 13, there is one in which a concavo-convex pattern is formed by providing a plurality of concave portions 56 on a sliding surface 53a which is an outer spherical surface of a bone head 53 (Patent Document 1). By forming the concavo-convex pattern, friction and wear can be reduced, and the life of the artificial hip joint is extended. In this case, the arrangement pitch of the recesses (0.8 mm to 1.6 mm), the depth of the recesses 56 (1 μm to 10 μm), the area ratio of the recesses 56 to the entire sliding surface (30% to 70%), the diameter in terms of a circle ( 0.2 mm to 0.8 mm), and the material is limited.

  Further, conventionally, as shown in FIG. 14, the inner surface (sliding surface) of the concave ball portion 55 of the acetabular socket 51 is provided with a high load region 60 where the maximum load point from the bone head 53 exists and the maximum load point. In some cases, the low-load region 61 is separated from the low-load region 61 and the recessed portion 62 is provided in the low-load region 61 (Patent Document 2). By providing the recessed portion 62, the lubricity can be sufficiently improved and local wear hardly occurs. In this case, the depth of the recessed portion 62 is 0.1 mm to 3.0 mm, and the area ratio of the recessed portion 62 is 3 to 50%.

Japanese Patent No. 3590992 JP 2011-87712 A

  When configured as described in Patent Document 1, the concave portion (dimple) generates equal pressure in a narrow region. At this time, only the positive pressure part contributes to the load capacity due to the occurrence of cavitation. However, since the positive pressure generation region is narrow, only a slight pressure increase can be obtained. For this reason, the dynamic pressure generation effect is small, and the oil sump effect contributes to the mixed lubrication characteristics, but hardly contributes to the fluid lubrication characteristics.

  Further, in Patent Document 2, since the fluid easily flows out from the wide recessed portion 62, the squeeze action due to the approach between the two surfaces is remarkably reduced, and the fluid lubrication characteristics may be deteriorated. Here, squeeze is a phenomenon in which, when the clearance between two surfaces decreases, pressure is generated by viscous resistance accompanying the outflow of the lubricating liquid in the clearance.

  In view of the above-described problems, the present invention provides an artificial hip joint that has a fluid lubricating film forming function with a minute clearance and generates less squeak noise and less wear.

  The artificial hip joint of the present invention is an artificial hip joint comprising a acetabular socket having a concave sphere portion and an artificial bone head that fits into the concave sphere portion of the acetabular socket and makes a relative sliding contact. An annular region having a periodic structure part composed of a plurality of fine grooves is provided on the sliding surface of the concave sphere part of the lid socket with the artificial bone head.

  According to the artificial hip joint of the present invention, by providing an annular region having a periodic structure portion on the sliding surface on the acetabular socket side with little change in the load application position, dynamic pressure is applied to sliding in all swing directions. And a fluid lubricating film can be formed.

  In a state of use in which the artificial bone head is fitted to the concave ball portion of the acetabular socket and is in relative sliding contact, the center of the annular region is within a range where the maximum load point for receiving the maximum load from the artificial bone head can exist. Preferably there is. As a result, a large dynamic pressure is obtained by introducing the fluid into the region where the maximum load point can exist. Here, the maximum load point is the sliding surface (inner surface) from the artificial bone head to the concave ball portion of the acetabular socket in the state of use in which the artificial bone head is fitted to the concave ball portion of the acetabular socket and is in relative sliding contact. ) Is the point that receives the maximum load.

  It is preferable that the fine grooves constituting the periodic structure portion are set so as to have an intersection angle of 30 degrees or more with the tangent line of the annular region. By setting in this way, the fluid is efficiently introduced into the sliding surface (between the inner surface of the concave ball portion of the acetabular socket and the outer surface of the artificial bone head).

  The average radius of the inner peripheral edge of the annular region is the contact radius of the Hertzian contact portion between the artificial bone head and the acetabular socket when the artificial bone head is fitted into the concave ball portion of the acetabular socket and is in relative sliding contact. It is preferable that it is 0.5 to 10 times.

  Even if the periodic structure portion is formed around the entire circumference of the annular region, the periodic structure portion may be intermittently formed in the annular region. In the case of being formed intermittently, the periodic structure forming portions and the non-forming portions are alternately formed along the sliding direction along the circumferential direction. As a result, pressure is generated at the boundary between the periodic structure forming portion and the non-forming portion in turning around the axis, and a pressure gradient is created in the sliding direction (this action is called a step effect).

  The periodic pitch of the periodic structure portion is preferably 10 μm or less, and the depth of the concave portion of the periodic structure portion is preferably 1.0 μm or less.

  The periodic structure portion is preferably formed in a self-organized manner by irradiating a linearly polarized laser beam with an irradiation intensity in the vicinity of the processing threshold, and scanning while overlapping the irradiated portion.

  The artificial hip joint of the present invention can form a fluid lubricating film in which a dynamic pressure is obtained with a minute clearance with respect to sliding in all swinging directions, can suppress generation of squeak noise, and has little wear. Can provide hip joints.

  By setting the center of the annular region to be within a range where the maximum load point for receiving the maximum load from the artificial bone head can exist, a large dynamic pressure can be obtained, and the generation of squeak noise and wear can be greatly reduced.

  By setting the fine groove so as to have an intersecting angle of 30 degrees or more with the tangent of the annular region, the fluid is efficiently introduced into the sliding surface, and a large dynamic pressure effect can be obtained.

  When the contact radius of the Hertz contact portion between the artificial bone head and the acetabular socket is 0.5 to 10 times, a large dynamic pressure effect by sliding can be obtained while suppressing a decrease in the squeeze action.

  By making the annular region constituting the periodic structure portion intermittent, a step effect is produced, and a large dynamic pressure effect can be obtained in turning around the axis.

By setting the periodic pitch of the periodic structure portion to 10 μm or less, side leakage of the lubricant can be suppressed redundantly, and an efficient dynamic pressure can be obtained. By setting the irregularities of the periodic structure to 1.0 μm or less, oil film fluctuation is small and high load capacity and rigidity can be obtained, and a decrease in squeeze action can be suppressed.

  If the periodic structure part is irradiated with linearly polarized laser light with an irradiation intensity near the processing threshold, and the irradiated part is overlapped and scanned in a self-organized manner, the submicron period is difficult to machine. A periodic structure having a pitch and unevenness depth can be easily obtained.

It is a perspective view of the acetabular socket of the artificial hip joint which shows embodiment of this invention. It is a simplified view of an artificial hip joint. It is an enlarged view of the periodic structure part formed in the concave ball part of a mortar socket. It is a simplified development view of the inner surface of the concave ball portion of the acetabular socket. It is a simplification figure of the laser surface processing apparatus for forming a periodic structure part. It is a simplified diagram showing a reciprocating pin-on-plate test apparatus used in an example. The pin test piece used for the reciprocating pin-on-plate test apparatus shown in FIG. 6 is shown, (a) is a simplified view of a mirror surface pin having no periodic structure part, and (b) has a periodic structure part. It is a simplified diagram of a periodic structure pin. It is a graph which shows the relationship between the sliding speed of a periodic structure pin and a mirror surface pin, and a friction coefficient. It is a graph which shows the relationship between the sliding stationary time of a periodic structure pin and a mirror surface pin, and a starting friction coefficient. It is a graph for demonstrating the definition of arithmetic mean roughness. It is a ring test piece used for a ring-on-disk test, (a) is a simplified view of a mirror ring in which sliding surfaces are intermittently formed along the circumferential direction, and (b) is a circumferential direction. It is a simplification figure of the periodic structure ring in which the periodic structure part is intermittently formed along. It is a graph which shows the relationship between the sliding speed of a periodic structure ring and a mirror surface ring, and a friction coefficient. It is a side view of the conventional artificial hip joint. It is a simplified development view of the inner surface of the concave ball portion of another conventional hip joint acetabular socket.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  As shown in FIG. 2, the hip prosthesis according to the present invention includes an acetabular socket 22 that is attached to the acetabulum of the pelvis 21, a stem 24 that is inserted into the medullary cavity of the femur 23, and an acetabular socket 22. And an artificial bone head 26 fitted to the concave ball portion 25. In addition, the stem 24 and the bone head 26 are connected via a neck portion 27.

  The acetabular socket 22 is a bowl-shaped body having a concave ball portion 25, and is fixed to the acetabulum of the pelvis 21 with bone cement or the like so that the open end face 28 faces outward. Further, the bone head 26 is formed of a spherical body, and is fitted into the concave ball portion 25 of the acetabular socket 22 to make a relative sliding contact.

  The stem 24 is made of a metal such as titanium, a titanium alloy, or a cobalt-chromium alloy, and the acetabular socket 22 and the artificial bone head 26 are made of the same metal as the stem 24, and further, ceramic (zirconia, alumina, etc.) or plastic ( Ultra high molecular weight polyethylene).

  As shown in FIGS. 1 and 4, an annular structure having a periodic structure portion 32 formed of a plurality of fine grooves on the inner surface (artificial head sliding surface 30) of the concave ball portion 25 of the acetabular socket 22. A region 31 is provided.

  As shown in FIG. 3, the periodic structure portion 32 is formed by alternately arranging minute concave portions 5 and minute convex portions 6 at a predetermined pitch. It is preferable that the concavo-convex pitch of the periodic structure portion 32 is 10 μm or less and the depth T of the concave portion 5 is 0.1 μm or more and 1 μm or less.

  The periodic structure portion 32 is formed in a self-organized manner by irradiating a linearly polarized laser beam with an irradiation intensity in the vicinity of the processing threshold, scanning the irradiated portion in an overlapping manner. Specifically, the femtosecond laser surface processing apparatus shown in FIG. 5 is used. A laser (eg, pulse width: 120 fs, center wavelength: 800 nm, repetition frequency: 1 kHz, pulse energy: 0.25 to 400 μJ / pulse) generated by a laser generator 11 (titanium sapphire femtosecond laser generator) is reflected by a mirror 12. It is folded back toward the work material W and guided to the mechanical shutter 13. At the time of laser irradiation, the mechanical shutter 13 is opened, the laser irradiation intensity can be adjusted by the half-wave plate 14 and the polarization beam splitter 16, the polarization direction is adjusted by the half-wave plate 15, and the condenser lens (focal length) : 150 mm) 17, the surface of the work material W on the XYθ stage 19 is condensed and irradiated. A femtosecond laser is a light source that compresses energy in an extremely short time unit of the order of femtoseconds (one thousandth of a second).

  When a workpiece (working material) W is irradiated with a linearly polarized laser beam at a fluence near the ablation threshold, pitches and groove depths on the order of wavelengths are caused by interference between incident light and scattered light or plasma waves along the surface of the processing material W. A grating-like periodic structure having a self-organization is formed perpendicular to the polarization direction. At this time, the periodic structure part 32 can be expanded over a wide range by scanning the femtosecond lasers while overlapping them.

  Laser scanning may be performed by moving the XYθ stage 19 that supports the processing material W while fixing the laser, or may move the laser while fixing the XYθ stage 19. Alternatively, the laser and the XYθ stage 19 may be moved simultaneously. FIG. 3 is a diagram obtained by imaging the periodic structure portion 32 formed by the femtosecond laser surface processing apparatus with an electron microscope.

  In this case, when the artificial bone head 26 is fitted to the concave spherical portion 25 of the acetabular socket 22 and is in relative sliding contact, the center O of the annular region 31 receives the maximum load from the artificial bone head 26. The point is within a possible range. For this reason, the maximum load point does not enter the annular region 31. The maximum load point on the outer surface of the artificial bone head 26 corresponding to the maximum load point on the inner surface of the concave ball portion 25 of the acetabular socket 22 is greatly displaced depending on the posture and movement of the user, but the maximum load point on the acetabular socket 22 side. Does not change much. For this reason, it is easy to provide the annular region 31 in the concave spherical portion 25 of the mortar socket 22.

  The fine grooves constituting the periodic structure portion 32 extend in the radial direction, and as shown in FIG. 4, the crossing angle θ with the tangent L of the annular region 31 is 30 degrees or more. In FIG. 4, the crossing angle θ is 90 degrees.

  By the way, the state of contact at a point when the load is 0 is called point contact, and these come into contact at a surface when a load is applied. A state of contact with a line when the load is zero, such as contact between a cylinder and a plane, is called line contact, and this also comes into contact with a surface when a load is applied. Contact on these surfaces is called Hertzian contact.

  For this reason, even in this artificial hip joint, when no load is applied, the inner surface (sliding surface 30) of the concave ball portion 25 of the acetabular socket 22 and the outer surface (sliding surface 35) of the artificial bone head 26 are in point contact. There will be contact with the surface if a load is applied. That is, the Hertz contact. Therefore, in the present invention, as shown in FIG. 4, the average radius Ra of the inner peripheral edge 31 a of the annular region 31 is 0.5 times the contact radius r of the Hertz contact portion 36 between the artificial bone head 26 and the acetabular socket 22. 10 times. The average radius of the inner peripheral edge 31a of the annular region 31 is Ra, the average radius of the outer peripheral edge 31a of the annular region 31 is Rb, and the width dimension (Rb-Ra) of the annular region 31 is 2 mm or more.

  According to the present invention, by providing the annular region 31 having the periodic structure portion 32 in the acetabular socket 22, a fluid lubricating film is obtained in which a dynamic pressure can be obtained with a minute clearance with respect to sliding in all swing directions. be able to. As a result, generation of squeak noise can be suppressed, and an artificial hip joint with less wear can be provided.

  In a state of use in which the artificial bone head 26 is fitted to the concave spherical portion 25 of the acetabular socket 22 and is in relative sliding contact, the center of the annular region 31 has a maximum load point that receives the maximum load from the artificial bone head 26. By setting it to be within the range, a large dynamic pressure can be obtained by introducing the fluid into the region where the maximum load point can exist, greatly reducing the occurrence of squeak noise and wear, and high quality. An artificial hip joint can be obtained.

  In addition, the fine grooves constituting the periodic structure portion 32 are set so as to have an intersecting angle of 30 degrees or more with the tangent line of the annular region 31 (inside the sliding surface (the inner surface of the concave ball portion 25 of the acetabular socket 22). And the outer surface of the artificial bone head 26), fluid (joint fluid) is efficiently introduced, and a large dynamic pressure effect can be obtained. If the crossing angle is less than 30, the effect of introducing fluid (joint fluid) is low and the dynamic pressure effect cannot be obtained so much.

  If the average radius R of the inner peripheral edge of the annular region 31 is 0.5 times to 10 times the contact radius r of the Hertz contact portion 36 between the artificial bone head 26 and the acetabular socket 22, the sliding is suppressed while keeping the decrease in the squeeze action low. A large dynamic pressure effect due to movement can be obtained. If it is less than 1 time, the annular region 31 enters the Hertz contact portion 36. For this reason, if it is less than 0.5 times, the annular region 31 enters too much into the Hertz contact portion 36, and if it exceeds 10 times, the annular region 31 is too far away from the Hertz contact portion 36. It is not possible to achieve the effect of “obtaining a large dynamic pressure effect by sliding while keeping the decrease in the pressure low”.

  By setting the periodic pitch of the fine structure to 10 μm or less, side leakage of the lubricant can be suppressed redundantly, and an efficient dynamic pressure can be obtained. By setting the unevenness of the periodic structure portion 32 to 1.0 μm or less, oil film fluctuation is small and high load capacity and rigidity can be obtained, and a decrease in squeeze action can be suppressed.

  When the periodic structure portion 32 is irradiated with linearly polarized laser light with an irradiation intensity in the vicinity of the processing threshold, and the irradiated portion is scanned while being overlapped, it is formed in a self-organized manner. A periodic structure having a periodic pitch and an unevenness depth can be easily obtained.

  By the way, in the said embodiment, although the periodic structure part 32 was formed over the perimeter, the periodic structure part 32 may be intermittently formed in the annular region 31 along the circumferential direction. In the case of being formed intermittently, the periodic structure forming portions and the non-forming portions are alternately formed along the sliding direction along the circumferential direction. As a result, pressure is generated at the boundary between the periodic structure forming portion and the non-forming portion. That is, a step effect is generated by the periodic structure forming portion and the non-forming portion, and a dynamic pressure can be obtained in turning around the axis. In addition, when providing the periodic structure part 32 intermittently, as for the arrangement pitch and the number of arrangement | positioning, a step effect will arise and it can change variously in the range which can obtain a dynamic pressure in the turning around an axis | shaft.

  As described above, the embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment, and various modifications are possible. For example, in the embodiment, when the periodic structure portion 32 is formed, Although a femtosecond laser which is a pulse laser is used, a pulse laser such as a picosecond laser or a nanosecond laser other than the femtosecond laser can also be used. Further, the acetabular socket 22 and the artificial bone head 26 may be slid by soft and soft, whether sliding by hard and hard using metal or ceramics, or sliding by soft and hard. It may be dynamic.

  A test using a reciprocating pin-on-plate test apparatus shown in FIG. 6 was conducted. The test using the reciprocating pin-on-plate test apparatus is a plate test piece 1 as a flat plate body, a pin test piece 2 as a disk body, and a pin test piece on the sliding surface 1 a on the upper surface of the plate test piece 1. 2 is mounted, and the pin test piece 2 is reciprocated linearly as indicated by an arrow X in FIG. In this case, the material of the plate test piece 1 and the pin test piece 2 was SUS440C, and the diameter D (see FIG. 7) of the pin test piece 2 was 5 mm. In addition, the plate test piece 1 was sized so that the pin test piece 2 did not protrude by the reciprocating motion of the arrow X in FIG. 6 (reciprocal pitch 6 mm).

Moreover, as the pin test piece 2, as shown to Fig.7 (a), the mirror surface pin 2A which does not have a periodic structure part, and the periodic structure pin 2B which has the periodic structure part 32 as shown in FIG.7 (b) 2 types were prepared. Here, the mirror surface pin 2A is obtained by finishing the surface roughness (arithmetic average roughness) Ra of the sliding surface 2a to about 0.02 μm. As shown in FIG. 10, the arithmetic average roughness Ra means that only the reference length is extracted from the roughness curve in the direction of the average line, the X axis is in the direction of the average line m of the extracted portion, and the direction of the vertical magnification. When the Y-axis is taken and the roughness curve is expressed by y = f (x), the value obtained by the following formula 1 is expressed in micrometers (μm).

  The periodic structure pin 2B is obtained by forming the periodic structure portion 32 on the outer peripheral portion of the sliding surface 2a. In this case, the land portion 40 (having the periodic structure portion) formed on the inner peripheral side of the periodic structure portion 32 is used. The surface roughness (arithmetic mean roughness) Ra of the portion not to be processed is finished to about 0.02 μm. The width (radial width) E of the periodic structure portion 32 was set to about 0.5 mm. (Since the periodic structure forming portion is φ4 mm to φ5 mm, E is 0.5 mm.) As a lubricant, PAO6 (poly-α-olefin: 37 ° C. which is not polar and is thermally and chemically stable) Viscosity of 31.3 cP) was used.

  The periodic structure portion 32 was formed by the femtosecond laser surface processing apparatus described in FIG. That is, the surface of the material was irradiated with a linearly polarized femtosecond laser at an energy density in the vicinity of the processing threshold and formed in a self-organized manner. As the periodic structure portion 32, a grating-like periodic structure having a periodic interval of about 700 nm and an unevenness depth of about 200 nm for the purpose of generating dynamic pressure was formed.

  For the mirror surface pin 2A and the periodic structure pin 2B, the pressure is set to 0.5 MPa, and the sliding speed is changed from 4 mm / s to 0. The relationship between the sliding speed and the friction coefficient was investigated while gradually decelerating to 1 mm / s. In order to investigate the influence on the ringing and squeeze effects, the starting friction coefficient (average friction coefficient of 0.1 ls after starting) was measured after the sliding speed was set to 4 mm / s and the stationary state was stopped for a predetermined time.

  FIG. 8 shows the relationship between the sliding speed and the friction coefficient of the mirror surface pin 2A and the periodic structure pin 2B. Due to the formation of the periodic structure, a reduction in the coefficient of friction was observed at all speeds. At this time, the friction coefficient ratio between the mirror surface pin 2A and the periodic structure pin 2B increases as the sliding speed increases, and the friction reduction effect by the periodic structure increases. The coefficient of friction of the periodic structure pin had a small variation (standard deviation) and a stable value. The generation of the dynamic pressure is caused by the fluid introduction effect that the groove of the periodic structure draws the fluid into the central portion and the step effect of the boundary between the periodic structure forming portion and the unformed portion. When the direction of the periodic structure becomes the circumferential direction, the fluid introduction effect disappears, and thus the generation of dynamic pressure is greatly reduced.

  FIG. 9 shows the relationship between the sliding stationary time and the starting friction coefficient of the mirror surface pin 2A and the periodic structure pin 2B. Regardless of the presence or absence of the periodic structure, the oil friction was lost as the sliding stationary time increased, so the starting friction coefficient increased, but the starting friction coefficient of the periodic structure pin was always lower than that of the mirror surface pin 2A. When the periodic structure is formed, the oil film tends to be washed away at rest, and the squeeze action cannot be denied. However, an oil film exists in the groove portion of the outer peripheral portion of the periodic structure, and the supply of the lubricating liquid at the time of startup is promoted. Therefore, dynamic pressure is generated at an extremely fast response speed at the time of start-up, and it is considered that the start-up friction coefficient is reduced due to the rapid recovery of the oil film. Therefore, in order to reduce the starting friction coefficient, it is necessary to set the gain of dynamic pressure generation due to the formation of the periodic structure to exceed the reduction of the squeeze action.

  For this reason, if the annular region 31 having the periodic structure portion 32 composed of a plurality of fine grooves is provided on the artificial bone head sliding surface 30 of the concave ball portion 25 of the acetabular socket 22, the reduction of the squeeze action is reduced. It can be seen that a large dynamic pressure effect by sliding can be obtained while suppressing, and an artificial hip joint excellent in slidability can be configured.

  A ring-on-disk test was performed. In this case, a fixed side test piece (not shown) made of a disk test piece and a rotation side test piece 41 made of a ring test (see FIGS. 11A and 11B) were used. A rotation side test piece 41 (41A) shown in FIG. 11A is provided with convex portions 42 arranged at a predetermined pitch along the circumferential direction on one surface, and the surface of the convex portion 42 is a sliding surface 42a. It is said. For this reason, the rotation side test piece 41 shown to Fig.11 (a) is called the mirror surface ring 41A. Moreover, the rotation side test piece 41 shown in FIG. 11B has the periodic structure portion 32 on the sliding surface of the convex portion 42. In this case, the periodic structure portion 32 is provided on the sliding surface of each convex portion 42 on the front side in the rotational direction, and the groove direction is the circumferential direction. For this reason, the rotation side test piece 41 shown in FIG.11 (b) is called the periodic structure ring 41B.

  The material of the fixed side test piece and the rotation side test piece 41 (41A, 41B) was SUS440C, and the surface roughness of the sliding surface of the convex portion 42 was finished to Ra of about 0.02 μm. The rotation side test piece 41 (41A, 41B) has an outer diameter D1 of 15 mm, an inner diameter D2 of 10 mm, and the outer diameter of the fixed side test piece is equal to or larger than the fixed side test piece. Set. Moreover, the periodic structure part 32 was formed with the femtosecond laser surface processing apparatus described in FIG. As the periodic structure portion 32 in this case, a grating-like periodic structure having a periodic interval of about 700 nm and an unevenness depth of about 200 nm was formed. As the lubricant, PAO2 (poly-α-olefin: viscosity at 37 ° C. of 4.6 cP) was used.

  With respect to the mirror ring 41A and the periodic structure ring 41B, the pressure is set to 0.5 MPa, and the relationship between the sliding speed and the friction coefficient is reduced while the sliding speed is gradually reduced from 81.5 mm / s to 3.3 mm / s. Examined. The results are shown in FIG.

  In the periodic structure ring 41B, due to the formation of the periodic structure, a reduction in the coefficient of friction was recognized at all speeds even during rotational sliding. At this time, the friction coefficient ratio between the mirror ring 41A and the periodic structure ring 41B increases as the sliding speed increases, and the friction reduction effect by the periodic structure portion 32 increases. Moreover, the generation of dynamic pressure is caused by the step effect between the periodic structure forming part and the non-forming part.

  The step effect is maximized in the circumferential direction where the direction of the periodic structure portion 32 is the same as the sliding direction, and is minimized in the radial direction orthogonal to the sliding direction. However, when the oil film thickness is 0.2 μm, it is calculated from the infinite groove number theory that a dynamic pressure of 20% to 70% of the periodic structure in the circumferential direction can be obtained even with the periodic structure in the radial direction. The direction of the structure needs to be set in consideration of the balance with the reciprocating sliding characteristics, but a periodic structure in the radial direction can also be used.

  If the fine grooves constituting the periodic structure portion 32 have an intersecting angle θ of 30 degrees or more with the tangent of the annular region 31, a large dynamic pressure effect can be obtained, and the periodic structure portion 32 is constituted. It can be seen that by making the annular region 31 intermittent, a step effect is produced, and a large dynamic pressure effect can be obtained in turning around the axis.

5 concave portion 22 acetabular socket 25 concave ball portion 26 artificial bone head 30 artificial bone head sliding surface 31 annular region 32 periodic structure portion 36 hertz contact portion

The artificial hip joint of the present invention is an artificial hip joint comprising a acetabular socket having a concave sphere portion and an artificial bone head that fits into the concave sphere portion of the acetabular socket and makes a relative sliding contact. the sliding surface of the endoprosthesis of the concave spherical portion of the lid socket, provided intermittently formed Ru annular region periodic structure portion constituted by a plurality of fine grooves along a circumferential direction, the annular region, Dynamic pressure is generated with respect to sliding in the swinging direction and turning around the shaft .

Periodic structure section Ru are intermittently formed in the annular region. In the case of being formed intermittently, the periodic structure forming portions and the non-forming portions are alternately formed along the sliding direction along the circumferential direction. As a result, pressure is generated at the boundary between the periodic structure forming portion and the non-forming portion in turning around the axis, and a pressure gradient is created in the sliding direction (this action is called a step effect).

Claims (9)

An artificial hip joint comprising a acetabular socket having a concave sphere portion, and an artificial bone head that fits into the concave sphere portion of the acetabular socket and makes a relative sliding contact;
An artificial hip joint characterized in that an annular region having a periodic structure part composed of a plurality of fine grooves is provided on a sliding surface of the concave sphere part of the acetabular socket with the artificial bone head.   In a state of use in which the artificial bone head is fitted to the concave ball portion of the acetabular socket and is in relative sliding contact, the center of the annular region is within a range where the maximum load point for receiving the maximum load from the artificial bone head can exist. The artificial hip joint according to claim 1, wherein the artificial hip joint is provided.   The artificial hip joint according to claim 1 or 2, wherein the fine groove constituting the periodic structure portion has an intersecting angle of 30 degrees or more with a tangent of the annular region.   The average radius of the inner peripheral edge of the annular region is the contact radius of the Hertzian contact portion between the artificial bone head and the acetabular socket when the artificial bone head is fitted into the concave ball portion of the acetabular socket and is in relative sliding contact. The artificial hip joint according to any one of claims 1 to 3, wherein the artificial hip joint is 0.5 times to 10 times as long as the hip joint.   The artificial hip joint according to any one of claims 1 to 4, wherein a periodic structure portion is formed all around the annular region.   The artificial hip joint according to any one of claims 1 to 4, wherein the periodic structure portion is intermittently formed along the circumferential direction in the annular region.   The artificial hip joint according to any one of claims 1 to 6, wherein a periodic pitch of the periodic structure portion is 10 µm or less.   The artificial hip joint according to any one of claims 1 to 7, wherein a depth of the concave portion of the periodic structure portion is 1.0 µm or less.   The periodic structure part is formed in a self-organized manner by irradiating a linearly polarized laser beam with an irradiation intensity in the vicinity of a processing threshold and scanning the overlapping part in an overlapping manner. The artificial hip joint according to claim 8.